As the demands for portable electronic products such as notebooks, video cameras and cellular phones are rapidly increased in these days, and development of electric vehicles, energy storage batteries, robots, satellites, etc. is under active progress, numerous studies are being made on high-performance secondary batteries capable of being repeatedly charged and discharged.
Currently, nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, lithium secondary batteries or the like are commercially available as secondary batteries. Among them, lithium secondary batteries are the center of interest because they hardly have memory effects and can be freely charged or discharged when compared with nickel-based secondary batteries. Advantageously, lithium secondary batteries also exhibit very low self-discharge and high energy density.
In particular, in these days, as carbon energies are gradually exhausted and the interest on environments is increased, hybrid vehicles and electric vehicles become the focus of the public attention not only in U.S.A., Europe, Japan, and Korea but also in all countries in the world. In such hybrid or electric vehicles, the most fundamental part is a battery that gives a driving force to a vehicle motor. Since the hybrid or electric vehicle may obtain a driving force by means of charging/discharging of the battery, the hybrid or electric vehicle may eliminate or reduce an exhausted pollutant while ensuring excellent fuel efficiency, and thus the hybrid or electric vehicle is used more and more.
However, the vehicle battery used for such a hybrid or electric vehicle may encounter severe circumstances frequently in the consideration that it is mounted to a vehicle, differently from batteries used for general portable electronic products. For example, in a case where a vehicle runs in a polar region or in a very cold winter, the battery should be operated though the temperature is very low. In addition, in a case where a vehicle runs at the equator or in a very hot summer, the battery should be operated though the temperature is very high.
If a high current flows in the battery so as to transfer a high driving force to a vehicle in an ultimately severe temperature circumstance, the high current may give a bad influence on the life and performance of the battery. In other words, the ultimately severe operation condition of the battery may shorten the life of the battery and weaken the performance in comparison to normal operation conditions. Nevertheless, in the conventional art, though a battery is exposed to severe operation conditions, relevant data is not provided to a driver or a repair man. For this reason, a vehicle driver or the like could not properly check that the life and performance of a battery are deteriorated since the battery is used in ultimately severe operation conditions. Thus, it is not easy to check a suitable time for repair or exchange, which may result in even a breakdown or failure of the battery or a malfunction of the battery. If the battery stops its function, a user may experience inconvenience since the vehicle cannot run. In addition, if the battery stops its function while the vehicle is running, a car accident may occur, which may seriously damage lives and properties. Moreover, since the operation history of the battery pack is not properly checked even when the vehicle or the battery pack is repaired, it is not easy to exactly diagnose the state of the battery pack.